1. Field of the Invention
This invention relates to an image taking system such as a digital camera which is capable of continuously taking images, a method of controlling the same and a computer-readable recording medium on which a program for causing a computer to execute the method of controlling the image taking system is recorded.
2. Description of the Related Art
There has been proposed a technique where two images are obtained prior to photographing both by the use of exposure without following stroboscopic light and by the use of exposure with following stroboscopic light and the amount of stroboscopic light to be emitted from the stroboscopic light source during photographing is controlled (or regulated) by the use of the two images. Such a technique where the amount of stroboscopic light to be emitted from the stroboscopic light source during photographing is calculated by the use of exposure without stroboscopic light and by the use of exposure with regulated stroboscopic light is generally referred to as the “light regulation calculation”. By exposing to light on the basis of the light regulation calculation, an image having a suitable brightness can be obtained.
When a continuous photographing is to be executed in a digital camera, exposures such as the ISO sensitivity, the stop, the shutter speed, whether the stroboscopic light is to be energized and the like are sometimes set for each photographing to different defaults. A plurality of times continuous emission of the stroboscopic light is sometimes required at the same time. When a continuous stroboscopic photographing is to be executed, it is required to charge the main capacitor each time the stroboscopic light is emitted. Accordingly, there is a problem that the continuous photographing with following stroboscopic light is reduced in the number of frames to be exposed in a unit time as compared with the continuous photographing without following stroboscopic light. Further, there is a fear that the amount of stroboscopic light to be emitted from the stroboscopic light source during later photographing can become short after a plurality of times continuous emission of the stroboscopic light.
For this reason, there is proposed a method in U.S. Pat. No. 6,636,263 where the amount of stroboscopic light to be emitted from the stroboscopic light source during continuous photographing and the amount of charge of the main capacitor required to realize the amount of stroboscopic light are estimated and when the time interval required to get the amount of charge of the main capacitor is longer than the time interval between the frames during the continuous photographing, the gain upon photographing is increased in order to compensate for the shortage of the amount of stroboscopic light.
When the technique disclosed in U.S. Pat. No. 6,636,263 is employed, the image quality is deteriorated since noise is increased as the gain is increased when the amount of stroboscopic light to be emitted from the stroboscopic light source becomes short. For this reason, it is conceivable that the stroboscopic light is continuously emitted without charging the main capacitor during a continuous photographing with following stroboscopic light and a remaining voltage in the main capacitor is measured each time the stroboscopic light is emitted, whereby the amount of stroboscopic light to be emitted from the stroboscopic light source is ensured by elongating the time interval between the frames.
However, the unit for measuring the remaining voltage in the main capacitor adds to the cost and complicates the circuitry to make the camera larger.